Hong Kong's new tax policy is significant not as of the specifics, but because of the change in the approach of the state in regulating its market economy. The tax plan to impose an extra stamp duty for "short-term" transactions is simple and straight forward, but the extent to which quick sales are driving Hong Kong's property market is in dispute. The fact that the Government has put forward this proposal shows that the government wants to use tax law to influence market behavior, writes Joseph Sternberg in The Wall Street Journal.